Interfacing with library instead of executables

[taoning]

In most of the functions, e.g. gendaylit(), the work is done by spawning a process to call an executable (gendaylit). When called repeatedly, the overhead of spawning a process starts to eat into the overall execution time.

To solve this, we'd need to build and interface through a shared library.

We would need to identify the tools/workflows that would benefit from this treatment.